Particulate matter sensors are used in internal combustion engines to monitor exhaust characteristics. There is a need for apparatus systems and methods that provide improved reliability and operability of particulate matter sensors particularly with respect to soot that results from incomplete combustion.
Typically, three types of particulate emissions can emit from unburned liquid fuel. A first type particulate includes the unburned or partially burned hydrocarbons, which are sometimes referred to as white smoke. A second type of particulate is soot, a particulate ash, which forms during gas-phase combustion. A third type of particulate is referred to as coke, which is also a particulate ash that forms during liquid-phase combustion.